Functional groups may be attached to a polymer chain according to two methods: by functionalizing during manufacture of the polymer, i.e. by copolymerizing with a monomer carrying the functional group, or by modifying the chain chemically. The latter method is the one most in use today, but the former has a number of advantages, one being that the number of manufacturing steps and thus side product formation can be reduced.
Porous or macroporous styrene materials are structures formed by agglomerated microspheres (100-200 nm) consisting in turn of cores (10-30 nm) (Jacobelli H., Guyot A., Angew. Makrom. Chem., 80, (1979), 31). Both between the cores and the agglomerates there are interconnected pores which provide for the large surface area of the polymer. These polymers have found a number of applications, especially within organic chemistry in the form of polymer bound catalysts, reagents and in chromatographic separation processes. Polymer bound enzymes, controlled dosage of medicines, pesticides and cosmetics are also used. The materials also find use for the purification of water, other liquids and gases.
Although the research regarding polymer bound reagents is very intensive, there are today only a few industrial applications in use. The reason for this is, from a polymer chemical point of view, three, namely diffusion restrictions within the polymer, insufficient mechanical characteristics and insufficient chemical inertness of the material. Diffusion restriction within the polymer makes the activity of the reagent low, if the diffusion rate into and out from the polymer becomes the rate controlling step. Insufficient mechanical strength makes the polymer break down, difficult to separate and re-use. Functional residues, side products and remaining double bonds can poison the polymer or break it down so that the functional groups and the activity are lost.
In order to obtain a pure product and good process economy it is important to keep the manufacturing steps as few as possible. Consequently, copolymerization of a monomer carrying the functional groups would be a feasible alternative for the synthesis of polymer, especially macroporous polymer supported species. However, until now it has not been possible to manufacture satisfactory products by copolymerization as the functional groups have, to a major degree, been locked within the polymer structure and are thus not available for reaction.
Macroporous polymers are mostly made by polymerizing a monomer and a crosslinking agent in the presence of a solvent which dissolves the monomers but not the polymer formed. Porous structures with interconnected pores can also be synthesized from water-in-monomer-emulsions in the presence of a surfactant. The latter method provides for very porous materials with larger pores and a more even, homogeneous pore structure than the former method.
An applicable method for the preparation of polymers with a high degree of porosity is described in J. Chem. Soc. Chem. Comm., 7, (1990), 1589, and in the EP-patent 0060138. Materials of this type are very attractive for the preparation of polymers with a grafted polymer layer within the pores.
In the publication J. Am. Chem. Soc., 112, (1990), 1263, Menger et al., there is disclosed a method for polymerizing styrene and divinyl benzene in a system were the water in monomer emulsion is a microemulsion. -- The term "microemulsion" has been defined (Danielsson et al., Colloids Surfaces, 3, (1981), 391) as a system consisting of water, oil and an amphiphilic compound, which forms a single optical isotrope and a thermodynamically stable solution. The microemulsion is made using as the surfactant i.a. sodium bis(2-ethylhexyl)sulfosuccinate (AOT).
In a later article, J. Am. Chem. Soc., 112, (1990), 6723, Menger et al. also described a method for controlling the location of the functional groups to the pore surfaces of the polymer. As the monomer carrying the functional group, a styrene derivative was used, having a, dimethyl amine group at the end of a chain attached to the phenyl group. Although the process described can be considered to give satisfactory products for some purposes, it has the drawback that the functional monomer used is excessively soluble in the styrene phase, wherefore its concentration in the pore forming water pools is reduced. Consequently the number of available functional groups in the final polymer is also reduced.
The aim of the present invention is i.a. to provide a new type of functionalizing monomers having superior and interesting complexing properties, and by means of which it is possible to achieve an increased degree of surface functionalization, and especially when used in the manufacture of macroporous styrene polymers, e.g. using the microemulsion polymerization technique.